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Temperature Dominance in Governing Nanoplastic Release and Leachate Composition from Polylactic Acid–Based Disposable Plastics
Summary
Researchers found that biodegradable polylactic acid (PLA) disposable cups released roughly 6 million nanoparticles per milliliter into water, substantially more than conventional polypropylene cups. Up to 55% of detected nanoparticles were self-assembled oligomer aggregates rather than true PLA particles, and water temperature was the dominant factor, with concentrations increasing nearly 100-fold between 50 and 70 degrees Celsius. The study suggests that hot beverage use in PLA cups drives the vast majority of human nanoplastic exposure from these products.
<title>Abstract</title> Nanoplastics released from biodegradable plastics have raised concern, yet their composition and release behavior remain largely unclear. Using polylactic acid (PLA)–based disposable containers, a common alternative to conventional plastics, we developed a quantitative analytical workflow to differentiate and characterize PLA-leached chemicals (PLCs), including PLA nanoparticles (NPs), PLA oligomers (OLAs), and lactic acid (LA). Simulated use of disposable cups (DCs) showed that PLA-DCs released ~6 million particles mL-1 NPs into water, substantially higher than conventional polypropylene (PP) DCs. More interestingly, up to 55% of detected NPs were OLA self-assembled aggregates rather than PLA NPs. Across use scenarios, water temperature was the dominant determinant: PLC concentrations increased nearly two orders of magnitude from 50 to 70 °C, accompanied by a shift from particulate to dissolved OLAs. Integrating national use behaviors with release parameters, global annual PLC exposure from PLA-DCs is projected to increase by 2 folds from 2021 to 2030. Although U.S. coffee cups account for 49% of PLA-DCs, hot coffee consumption contributed >99% of exposure, whereas in China, despite coffee cup consumption being only 20% of the U.S., hot water use in PLA-DCs still resulted in ~80% of the U.S. exposure. These findings highlight the need to establish NP and oligomer release as a new benchmark for evaluating biodegradable disposable plastics and to redefine safe-use temperature thresholds.
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